was then beneath southeastern oregon , induced eruptions from ste ##ens and nearby vents about 17 million years ago , in the miocene . the vents produced a series of lava flows that spread across the land now known as the trout creek mountains . eruptions from the ste ##ens volcano lasted for about one million years , and at least 70 separate lava flows occurred . under the resulting basalt rock lie much older meta ##morphic rocks that may be related to some of the triassic age formations of the blue mountains in northeastern oregon . within these meta ##morphic rocks are di ##ori ##te and gran ##od ##ior ##ite int ##rus ##ive bodies which were presumably int ##rud ##ed during the cretaceous period . the broad
was then beneath southeastern oregon, induced eruptions from steens and nearby vents about 17 million years ago, in the miocene. the vents produced a series of lava flows that spread across the land now known as the trout creek mountains. eruptions from the steens volcano lasted for about one million years, and at least 70 separate lava flows occurred. under the resulting basalt rock lie much older metamorphic rocks that may be related to some of the triassic age formations of the blue mountains in northeastern oregon. within these metamorphic rocks are diorite and granodiorite intrusive bodies which were presumably intruded during the cretaceous period. the broad